JPH02258014A - Apparatus for treating flue gas - Google Patents

Abstract

PURPOSE:To suppress corrosion and abrasion of electrodes to a minimum and to operate a flue gas treatment steadily for a long time by covering the first and the second electrodes with dielectric bodies in a vessel for glow discharge plasma reaction. CONSTITUTION:A serrate electrode 10 and a plate electrode 11 are set opposite to each other in parallel to a gas flow in a reaction vessel 5, which is opened at its both ends, and dielectric bodies 12, 13 are arranged so as to cover surfaces of the electrodes 10, 11 for the purpose of preventing them from being in direct contact with a flue gas. If the flue gas is introduced into the plasma reaction vessel 5 together with ammonia and an electric power is supplied from an electric source 8 to the serrate electrode 10 and the plate electrode 11, a glow discharge plasma of the flue gas containing ammonia is generated between the dielectric bodies 12 and 13 and NO, NO2 and SO2 in the flue gas are converted into N2, S and H2O. Corrosion and abrasion of the electrodes do not take place in this case, as the flue gas containing ammonia is not in direct contact with the serrate electrode 10 and the plate electrode 11. It is possible, therefore, to generate a steady glow discharge plasma for a long time.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention is directed to reducing nitrogen oxides (NO, Oxide (s
The present invention relates to an exhaust gas treatment device using glow discharge plasma that can effectively remove oxygen in a large amount.

[Conventional technology]

FIGS. 3 and 4 are explanatory diagrams of a conventionally used exhaust gas treatment apparatus using glow discharge plasma. With this device, for example, NO in the exhaust gas of a diesel engine can be removed.
An example of processing x will be explained.

In FIG. 3, exhaust gas from a diesel engine 101 is introduced into a cycle collector 103 via an exhaust pipe 102 to remove dust, and then introduced into a plasma reaction vessel 105K via an exhaust pipe 104. N in the plasma reaction vessel 105
The Ox is treated and discharged through the discharge pipe 101.

As shown in detail in FIG. 4, the plasma reaction vessel 105 has sawtooth electrodes 110, flat plate electrodes 111, . A dielectric 109 is provided.

A high voltage is applied from the power source 106 to the sawtooth electrode 110 and the flat plate electrode 111 to turn the exhaust gas into plasma, thereby removing NOx in the exhaust gas according to the following principle. That is, the exhaust gas is turned into plasma by the atmospheric pressure glow discharge phenomenon that occurs between the sawtooth electrode 110 and the flat plate electrode 1110.

For example, NOx causes the following chemical reaction.

2NO, -1 → 2NO+ 02-Mountain・(1) 2NO+
02-→N2+ 20□・------(21) Plasma is caused by an external electric field [accelerated high-energy electrons collide with gas molecules, excited molecules, excited atoms free radicals, ions, neutral particles, etc. It is an ionized gas mixed with the above (
1) , (In formula 21, it is thought that the NO element that has obtained an energy of several eV to several tens of eV becomes a chemically active species, and as a result of a complex reaction, it becomes N2 and VO□.

[As mentioned above, the exhaust gas from the engine is heated to atmospheric pressure.
When plasma is generated using the discharge phenomenon, (No +
No□) concentration of about 50 to 200- and 100It
In a flow rate range of approximately /i, a NOx removal rate of 80 to 90% can be achieved when the plasma generation power, that is, the power supplied from the power supply 106 is in the range of several watts to several 10 watts. Therefore, it is being used as an exhaust gas control device for various combustion devices such as boilers, gas turbines, and diesel engines.

[Problem that the invention seeks to solve]

The above-mentioned conventional apparatus has a problem in that when used continuously for a long time, the sawtooth electrode and the flat plate electrode corrode and wear out, making it difficult to generate glow discharge plasma and significantly reducing the NO removal rate.

[Means to solve the problem]

In order to solve the above problems, the present invention takes the following measures. In other words, in an exhaust gas treatment device that uses glow discharge plasma to treat nitrogen oxides and/or sulfur oxides in exhaust gas, the inlet and outlet a cylindrical reaction vessel having a cylindrical shape, a flat first electrode disposed within the reaction vessel with its surface along the gas flow direction, and a serrated surface disposed opposite to the first electrode. a second electrode having a diameter of 5g2, a first dielectric covering the surface of the first electrode, a dielectric covering the front page of the second electrode, and a second electrode covering the surface of the first electrode and the second electrode. Means for applying a voltage to the electrodes and an anthonia supply device coupled to the inlet of the reaction vessel are provided.

[Effect]

By the above means, a buffer gas (
After a very small amount of ammonia is mixed into the exhaust gas (as a buffer gas), the exhaust gas is introduced into the reaction vessel.

A high voltage is applied from the power supply between the first electrode and the second electrode, generating glow discharge plasma, and the energy promotes the chemical reaction of formula (31 or 6) described in the examples, and /or the bow is removed.

At this time, since the first and second electrodes are covered with a dielectric material, they do not come in contact with the exhaust gas, so they do not corrode or wear out.

Therefore, stable exhaust gas treatment can be performed over a long period of time.

〔Example〕

An embodiment of the present invention is shown in FIGS. 1 and 2 (a), (kl
This is explained by:

Note that the description of the portions described in the conventional example will be omitted to avoid redundancy, and the description will mainly focus on the portions related to the present invention.

In FIG. 1, reference numeral 1 indicates an object for taking measures against exhaust gas pollution in a general-purpose combustion furnace. 3 is a dust remover, 2 is an exhaust pipe that transfers the exhaust gas from the general-purpose combustion furnace 1 to the dust remover (cyclone collector, etc.) 3, 5 is a plasma reaction vessel, and 4 is a plasma reactor for the exhaust gas from the dust remover 3 An exhaust pipe for transporting ammonia to the reaction vessel 5; 6 a power source for applying plasma generation power to the electrodes of the plasma reaction vessel 5; 7 an exhaust gas output pipe connected to the plasma reaction vessel 5; 17 is an ammonia supply pipe connected to the discharge pipe 4.

The plasma reaction vessel 5 will be explained in detail with reference to FIGS. 2(a) and 2(b).

In a cylindrical plasma reaction vessel 5 with both ends open, a sawtooth electrode 10 and a plate electrode 11 facing each other are provided so as to allow gas to flow on the surface thereof. In addition, the dielectric material 13 is a sawtooth electrode 10.
The surface of the plate-shaped electrode 11 is covered with covers 5 and 5. Opposing surfaces of these dielectrics 12 and 13 are planar.

In addition, the sawtooth electrode 10 and the plate electrode 11 are dielectrically closed, 13
The structure is such that it does not come into direct contact with exhaust gas.

In the above configuration, ammonia is introduced from the ammonia supply device 16 into the plasma reaction vessel 5 together with the exhaust gas at a flow rate of several A/- to several 101/-.

When power is supplied from the plasma generation power source 6 to the sawtooth electrode 1o and the plate electrode 11, a gap between the dielectric 130 and the sawtooth electrode 1o is generated.
Plasma of exhaust gas containing ammonia is generated.

This plasma is a glow discharge plasma, which excites and dissociates gas molecules such as ammonia, NOx, and SOx, and makes them chemically active. This K causes the chemical reaction described below.

NH3+ electron energy approximately 6.4 eV →N)12
+ H60, (3) 2NO2 + electron energy approximately 9.5
eV →2NO+02-(43NH2+NO-→N2
+H20...(5)2NH2+ So□-+ S +
N2+ 2H20-(6) Equations (3) to (6) above are based on the assumption that No. This means that it becomes S and H2O. In this case, as mentioned above, the exhaust gas containing ammonia does not come into direct contact with the sawtooth electrode 10 or the plate electrode 11 (it only comes into contact with the dielectric material (e.g. glass, ceramics, etc.) 12.13). In particular, since there is no contact with ammonia), there is no corrosion or wear of the electrodes, and stable glow discharge plasma can be generated for a long time.Also, since it is a dielectric material and the surface of 130 is flat, there is little frictional resistance of exhaust gas (such as soot and dust). Less adhesion of by-products such as ammonium sulfate.

According to the apparatus of this embodiment, stable exhaust gas treatment can be performed for more than 10 times as long as the conventional apparatus.

In addition, although the treatment of exhaust gas containing NQJ: and Sox has been described above, this example deals with the treatment of exhaust gas containing NQJ: and Sox.
It can also be applied to the treatment of exhaust gas containing only O-works.

〔Effect of the invention〕

As explained above, according to the device of the present invention, corrosion and wear of the electrodes, which were unavoidable in conventional devices, can be suppressed to a minimum, and exhaust gas treatment can be performed stably for a long time. Therefore, it has extremely high industrial value as an exhaust gas outlet pipe and/or a SO treatment removal device.

[Brief explanation of drawings]

FIG. 1 is an overall configuration diagram of an exhaust gas treatment apparatus using an apparatus according to an embodiment of the present invention. FIG. 2 is a sectional view of the plasma reaction vessel of the same embodiment. FIG. 3 is an overall configuration diagram of an exhaust gas treatment device using a conventional device. FIG. 4 is a sectional view of the plasma reaction vessel of the conventional apparatus. 1... Combustion furnace, 2... Exhaust pipe, 3... Dust remover. 4... Exhaust pipe, 5... Plasma reaction vessel, 6...
power supply. 7... Exhaust gas outlet pipe, 10... Serrated electrode. 11... Flat plate electrode* 12-13...
dielectric. 16... Ammonia supply device, 17... Ammonia supply pipe. 18...Exhaust gas inlet pipe.

Claims (1)

[Claims] An apparatus for treating nitrogen oxides and/or sulfur oxides in exhaust gas using glow discharge plasma, which includes a cylindrical reaction vessel having an inlet and an outlet, and a surface parallel to the gas flow direction within the reaction vessel. a first electrode in the form of a flat plate, provided opposite to the first electrode and having a sawtooth surface; and a first dielectric covering the surface of the first electrode. and a second dielectric covering the surface of the second electrode;
An exhaust gas treatment device comprising means for applying a voltage to the first electrode and the second electrode, and an ammonia supply device coupled to an inlet of the reaction vessel.